Answer
Keep in mind that temperature is the average kinetic energy of the particles in a
substance, whereas heat is the total energy of all the particles. The air and
water may have particles moving the same speeds, but the water has more heat
because there are more particles.

Picture it this way. The ice melts as fast moving particles slam into the slow
moving ice particles. As in any collision, some of the energy is transferred to
the ice particle, and with its new energy it can break out of the crystal and flow
as a liquid water molecule.

To make the ice melt faster, you can use hotter (faster moving) particles to slam
into it. This is why the ice melts faster on a hot day than a cold one.
Alternatively, you can just use more collisions. The water is much more dense than
the air, with many more particles per cubic millimeter. Thus even though the water
molecules have the same kinetic energy as the air particles, there are many more of
them hitting the ice each second, and the ice melts faster.
Answered by:
Rob Landolfi, Science Teacher, Washington, DC